Coupled Simulation of Hydrate-Bearing and Overburden Sedimentary Layers to Study Hydrate Dissociation and Methane Leakage

Methane leakage during natural gas hydrate (NGH) exploitation is one of the important challenges restricting its safe development, which necessitates further investigation. However, only a few experimental studies have been conducted to characterize the relationship between methane (CH4) leakage and NGH exploitation. The CH4 leakage mechanism and controlling factors in the hydrate dissociation process are still unclear. A coupled simulator has been developed to study the CH4 hydrate exploitation and the possible leakage of CH4. The new system overcomes the difficulty of constructing hydrate-free overlying strata and seawater in previous studies and can simulate the in situ natural environment containing hydrate reservoirs, overlying strata and overlying seawater as well. In addition, the simulator integrates the spatial distribution of temperature, pressure and electric resistance in hydrate reservoir systems, and allows for the visual monitoring of the overlying strata and the sampling of overburden gas and liquids. The effectiveness of the coupled simulations was verified through experimental testing. The coupled simulations allowed for the characterization of the CH4 leakage mechanism and can be used to develop safe strategies for NGH exploitation.